In packing machines which make packages having a wrapper sleeve envelope, the sheet from which the wrapper sleeve is made has, as a rule, at least two layers. In the finished package, the outer layer has a higher melting point than the inner layer to provide for an easy transverse sealing and severance of the packages. The temperature of the sealing shoes is maintained at a temperature which is below the melting temperature of the outermost layer, but above the melting temperature of the innermost layer. The individual, interconnected package sleeves may be severed by a knife integrated into one of the sealing shoes.
A sealing and severing apparatus of the above-outlined type is described, for example, in published International Application WO 96/17720. Such apparatuses, however, are less adapted for packages which have wrapper sleeves consisting of a single material (monofilms), for example, of low-pressure polyethylene, because such films tend to stick to the sealing (welding) shoes.